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March 6, 2012

Invasive Species Put Antarctic Natives At Risk

by editor

As temperatures warm along Antarctica´s outer fringes, it allows for invasive plants and organisms to be carried in inadvertently by visiting scientists and tourists, putting the pristine ecosystem at risk, researchers have found.

An international team of researchers, writing in the Proceedings of the National Academy of Sciences (PNAS), said they scoured the clothes and boots of those visiting the southernmost continent and found that most were carrying plant seeds.

The risks from these biological stowaways will increase as the icy continent continues to thaw due to climate change, they report.

Lead author, Steven Chown, of Stellenbosch University in South Africa, said that Antarctica´s pristine ecosystem is fast changing. Over the past few decades, human activity has increased significantly, with 40,000 tourists and scientists visiting the continent in the 2007-08 summer season alone.

Chown and colleagues, wanting to see the clear picture of how significant the issue is, surveyed nearly 5,700 tourists, scientists, crew and support staff during the 2007-08 Antarctic summer season. They also vacuumed clothes, bags and travel gear of about 850 people. After all was said and done, the researchers found 2,686 stowaway seeds that they identified by species using photographs from plant databases.

With the analysis complete, Chown estimated that more than 70,000 seeds could have made their way onto the continent stowed away on clothes, shoes and gear during the 2007-08 summer season. Each visitor brought an average of 9.5 seeds, the study estimated.

The team said the rates were much higher for scientists, however; nearly 40 percent of scientists at research stations brought seeds with them, double the rate of tourists. And scientists doing field research brought even more in.

“What we found was that people´s boots and bags were the things that had most material attached,” Kevin Hughes from the British Antarctic Survey told Richard Black of BBC News. “I guess the tongue of the boot is an ideal place for seeds to be caught when you´re tying up your laces; but we did find them in various bits of clothing as well.”

Roughly half of the seeds were carried in come from cold climates elsewhere, such as the Arctic or the Alps, which makes them good candidates for thriving in the harsh polar ecosystem.

Antarctica is generally thought of as this vast ice-covered continent, and “there´s no chance that things are going to establish there,” Chown told Amina Khan of the Los Angeles Times. But that´s not the case, he noted. “[They´re] forgetting that probably less than 1 percent, but still a significant area, is ice-free - some of that´s in the peninsula region, and it´s been warming very quickly.”

The Antarctic Peninsula has warmed by about 4.8 degrees F over the past half century, much faster than the global average. As a result, ice is quickly melting.

Many islands in the sub-Antarctic region have already seen significant ecological changes due to the introduction of invasive species, such as dandelions and mouse-eared chickweed, that have been carried in either accidentally or deliberately. The team believes the Antarctic Peninsula and its outlying areas could see similar changes in the coming decades.

“Antarctica has a native ecology - a very well-established microbial ecology, and on the peninsula it has two species of indigenous plants,” Chown told BBC News. “And it will be changed by species coming in.”

The marine environment around the coast of Antarctica is changing too, with giant crabs establishing themselves in waters that were previously too cold to thrive in.

Antarctica´s ecosystem, an environment that has remained undisturbed for perhaps the past million years, could be altered by new invasive species killing off the native plants, Peter Convey, a terrestrial ecologist with the British Antarctic Survey, told the Los Angeles Times.

Plants, such as tumbleweed and kudzu can spread like wildfire, said Convey, who was not involved in the study. These invasive plants can easily establish themselves and drive out native species.

While most of the seeds found in the clothing and bags of those visiting originated in South America, a large number came from the Northern Hemisphere, many of those coming from cold regions that would make them suitable for establishing a foothold in the warmer regions of Antarctica.

The scientists referred to one region of Antarctica -- Deception Island, about 60 miles northwest of the peninsula -- that has already been colonized by two invasive grass species and two springtails -- tiny animals that live in topsoil and leaf litter. On the western slopes of the peninsula itself, the grass species Poa annua has established itself close to four research stations. It has also taken over several sub-Antarctic islands where it dominates vegetation.

The researchers point out the need for measures to be taken as soon as possible to tackle invasive species that have already taken root there, and to prevent the arrival of future stowaways.

Hughes has already “eradicated” one species of invasive plant from Deception Island, simply by pulling up the single specimen found there. But for more widespread species, it is probably already too late.

The International Association of Antarctic Tour Operators (IAATO), which covers most companies in the area, takes measures to ensure any visitors to the continent arrive seed-free; and some other scientific organizations have similar requirements.

“We can use guidelines for vehicles, make sure cargo hasn´t got seeds and invertebrates on it, make sure clothing is clean and that we bring fresh boots,” Hughes told BBC. “[However,] I think it´s safe to say that wherever people go, it´s inevitable that they bring other species with them; and no matter what we do, our best efforts will only reduce the rate at which species are introduced, we´ll never prevent it altogether.”

While many seeds are inadvertently carried in by tourists and scientists, it is likely that many seeds are also arriving on the peninsula, carried on the wind from South America.

But, Chown argued, there is still a human element to this scenario in the fact that for these seeds to establish themselves they need the right climatic conditions that have been created largely through humanity´s production of greenhouse gases.

If nothing is done, Chown added, parts of Antarctica´s coastal peninsula may look very much like many of the sub-Antarctic islands within a hundred years.

Chown said while the study focused mainly on invasive plants, animals could become an even greater problem on the Antarctic islands as the climate warms.

“If rodents ever got in, they´d be a real pest because rats have a habit of feeding on birds – and there´s huge, vast bird colonies in Antarctica,” he told The Los Angeles Times.